The present invention relates to an hydraulic tensioning tool for tensioning reinforcing cables, rods and like devices in concrete structures, comprising a first working piston-cylinder device which includes a tensioning cable-holder, and a second working piston-cylinder device which includes a cable lock for anchoring the cable subsequent to tensioning the same.
Tools of the aforesaid kind are used for tensioning reinforcing cables and like devices in prestressed concrete beams and like structural components manufactured en mass in separate beam beds provided with devices for anchoring the cables at both ends thereof. Prior to setting of the concrete the cables are stretched to a given tension and extension and are held in the concrete mass until the concrete has solidified to firmly anchor the cables therein, whereafter the cables are severed close to the end surfaces of the beams. When tensioning the cables of respective concrete beds, the tensioning tool is moved manually from cable to cable, and since a beam often contains twenty or more such cables it will be seen that high demands are placed on the reliability of the tool and its ease of handling. The tools used today, however, are very unsatisfactory in several respects. For example, the cable holder is difficult to reach for cleaning or maintenance purposes and the presence of many movable components equipped with seals and packings etc. which are subjected to constant wear means that the tool must be serviced regularly at short intervals. Furthermore it is difficult to control and regulate extension of the cable, which is a serious drawback since when tensioning a cable in the present context it is necessary to control both the tensioning load applied thereto and the extension created therein.
Accordingly an object of the invention is to provide a tool of the aforesaid kind with which the disadvantages encountered with known tools are overcome, This object and further objects will be apparent from the following description of the invention, from which the advantages afforded by the invention will also be understood.